1. Field of the Invention
The present invention relates generally to a dye for recording layer of the high density recordable disc, especially to a dye that is simple in synthesis and purification, cost efficient and applicable to recording layer of the high density recordable disc when prepared appropriately.
2. Description of the Prior Art
A storage medium must have the advantages of higher density, smaller size and lower cost in order to meet the demand for the circulation of information in the quickly developed era nowadays. As magnetic storage medium is not capable to satisfy these requirements, optical storage medium is greatly sought for as an alternative. Optical recording disc is growing very quickly in global market, thus developing cheaper and better quality optical recording materials are the goal of the invention.
Cyanine dyes, phthalocyanine dyes and azo dyes are three commonly used dyes for recording layer of the optical recording disc. The prior art dyes claimed in U.S. Pat. No. 5,958,087 and applied to recording layer of the optical recording disc are cyanine dyes with a refractive index n between 1.6 to 4.0 and an extinction coefficient between 0.01 to 0.45. The prior art dyes claimed in U.S. Pat. No. 6,169,721B1 and applied to recording layer, with an absorbency between 0.65 to 0.75, of the high density optical recording disc are azo dyes. In other words, the prior art technologies use either cyanine dye series or aze dye series as the recording material for optical recording discs. However, since the cost of such dyes is high and the steps for the synthesis and purification of such dyes are complicated, they are not capable to meet the huge demand of the market. It is, therefore, a tendency to use a dye that is cost efficient, simple in synthesis and purification, and applicable to high-density recording layers.
The primary objective of the present invention is to provide a rhodamine dye for recording layer of the high density optical recording disc in order to solve and remove the aforementioned problems.
The second objective of the present invention is to provide a rhodamine dye for recording layer of high density optical recording disc; the dye is simple in synthesis and purification and cost efficient, being capable to reduce the production cost substantially.
To achieve the aforementioned objectives, the present invention provides a rhodamine dye for recording layer of the high density optical recording disc, which has a chemical structure as shown in (I): 
where Xxe2x88x92 represents an acid anion and R represents a benzoic acid group, benzene sulfonic acid group or benzoic ester group. The dye of the present invention is applicable to recording layer of the high density optical recording disc after prepared appropriately.